1. Field of the Invention
The present invention relates to an input device, and more particularly to an input device suitable for electronic equipment having operation keys small in number.
2. Description of the Related Art
Conventional electronic equipment contains a microcomputer to allocate a single key among a plurality of processes. The microcomputer allows switchover among a plurality of states and determines a process to be executed in accordance with a combination of the selected state and the pressed key. Therefore, the microcomputer cannot determine a process to be executed unless the state selected when a key is pressed is not identified.
For example, a conventionally known key input device includes a key matrix portion including an ID code generating circuit, and a code conversion portion. The code conversion portion performs key-scan on the key matrix portion using an X bus for strobe signal output and a Y bus for key address input. The code conversion portion takes in an ID code from the Y bus through an ID code identifying portion. In this key input device, an ID code is set by using a particular signal output from the X bus initially or at the start of key-scan to temporarily clamp a particular line of the Y bus at a prescribed logic level.
The conventional key input device outputs the ID code to the Y bus initially or at the start of key-scan and therefore cannot perform ID code setting and key-scan simultaneously. Thus, the ID code has to be set every time the microcomputer of the electronic equipment changes states. Accordingly, a prescribed time is required before key-scan is started.